Non-symmetric multiple layer injection molded products and methods

ABSTRACT

A mold for molding an injection molded article comprises a mold cavity with a non-symmetrical portion. At least one flow leader in the non-symmetrical portion of the cavity produces a symmetrical flow boundary in a multilayer flow downstream of the non-symmetrical portion of the mold cavity. The at least one flow leader may be a variable thickness flow leader or may alternatively be a plurality of flow leaders having a flow path length that differs from the flow path length of an adjacent flow leader by no more than about 15%. The multilayer flow comprising an inner layer, an outer layer, and an interior layer. Co-injection molding apparatus and methods that may use the foregoing mold are disclosed. Similarly, co-injection molded articles and containers that may result from the foregoing mold, apparatus, and methods are disclosed.

FIELD OF THE INVENTION

Embodiments taught herein relate to multiple layer injection moldedproducts. In particular, the embodiments relate to multiple layerproducts having non-symmetric configurations and an interior layer of adifferent material than other layers.

BACKGROUND INFORMATION

Injection molded articles are used for a variety of purposes. Plasticinjection molded products are commonly made from materials such aspolyethylene terephtholate (PET) or polypropylene (PP). In the case ofarticles 10 such as shown in FIG. 1 that have non-symmetric shapes(relative to the location of the injection gate 15), a flow leader 20,e.g., a local increase in thickness from the nominal part thickness, areused to compensate for the differences in mold flow lengths in differentdirections from the injection gate 15.

Plastic materials such as PET and PP are gas (e.g., oxygen, nitrogen,etc.) permeable. For applications in which gas permeability isundesirable, for example, food products, medicines and other substancesand products that degrade upon gaseous exposure, a barrier material isco-injected with the plastic material. Typically, the barrier material,such as Ethyl Vinyl Alcohol (EVOH), is injected at the interior of thePET/PP material stream, forming an EVOH interior layer in the moldedproduct.

The present inventor has attempted to form non-symmetric co-injectionmolded containers containing such an interior layer using knownnon-symmetric molding technologies, e.g., utilizing a flow leader, yetthe resulting articles do not exhibit sufficient gas-impermeability. Theinventor has found that when using conventional flow leadertechnologies, the interior layer does not sufficiently extend throughoutthe molded product to prevent detrimental gas permeation. Even when onlysmall areas of the article do not contain the barrier material or asufficiently thick barrier material, substantial permeation occurs.

SUMMARY OF THE INVENTION

Embodiments taught herein address the aforementioned disadvantages ofknown non-symmetric molding technologies including conventional flowleader technology. Exemplary molds and apparatus taught herein featureimproved flow leader technology that can be used in a co-injectionmolding process to produce a non-symmetrical molded plastic article withsuperior coverage of its interior material layer. Exemplary molds,apparatus, methods, and non-transitory computer readable programs aretaught herein to cause an interior core of material to flow in a mannerthat result in a non-symmetrical molded plastic article with barriercoverage extending between 95% and 100% of the entire surface areawithin a sealed or sealable portion of the article. The exemplary molds,apparatus, methods, and non-transitory computer readable programs taughtherein are well suited for use in forming symmetrical molded plasticarticles and asymmetrical molded plastic articles with barrier coverageextending between 99% and 100% of the entire surface area within thesealed or sealable portion of the article. Some exemplary articlesinclude containers with an open end that may be sealed using a heatsealing methodology.

In one aspect, a mold for molding an injection molded article comprisesa mold cavity with at least one flow leader in a non-symmetric portionof the mold cavity. The at least one flow leader may comprise aplurality of flow leaders defining different thicknesses and/orconfigurations in a non-symmetrical portion of the mold cavity. Amultilayer flow comprises an inner layer, an outer, layer, and aninterior layer. The at least one flow leader produces a symmetrical flowboundary in the multilayer flow downstream of the non-symmetricalportion of the cavity.

In another aspect, a co-injection molding apparatus comprises a mold anda first injection gate. The mold defining a mold cavity having at leastone flow leader in a non-symmetrical portion thereof. The firstinjection gate is configured to co-inject at least one first and secondflowable materials into the mold cavity and through the at least oneflow leader. The at least one flow leader is configured to produces asymmetrical flow boundary downstream of the non-symmetric portion of thecavity. The apparatus thereby forms a molded article comprising thefirst and second flowable materials. The second flowable material isinterior to the first flowable material in the article. Due to the atleast one flow leader in the mold and the resulting symmetrical flowboundary, the apparatus may produce molded plastic articles with aninterior layer embedded within greater than 95% of the entire surfacearea of the article. In the foregoing aspect, the apparatus may define64 or more mold cavities.

In another aspect, a co-injection molding apparatus comprises aplurality of injection gates and a mold defining a mold cavityconfigured to form a molded article comprising a plurality of opencontainers. The mold cavity comprises a non-symmetrical portion that isnon-symmetrical with respect to the plurality of injection gates and atleast one flow leader in the non-symmetrical portion. The plurality ofinjection gates are configured for co-injection of a first flowablematerial and a second flowable material into the mold cavity and throughthe at least one flow leader to form the molded article with the firstand second flowable materials. The second flowable material is interiorto the first flowable material. The at least one flow leader isconfigured to produce a symmetrical flow boundary in the first andsecond flowable materials downstream of the non-symmetrical portion. Inthe foregoing aspect, the plurality of open containers may comprise 32open containers, 64 open containers, an intermediate number of opencontainers between 32 and 64 open containers, or more than 64 opencontainers.

In another aspect, a method of molding a multiple layer articlecomprises injecting at least one first flowable material into a moldcavity configured to form a molded article from the at least one firstflowable material. The mold cavity comprises a nonsymmetrical portionrelative to an injection location of the at least one first flowablematerial. The method further comprises co-injecting at least one secondflowable material into the mold cavity and interior to the at least onefirst flowable material. The method further comprises modifying the flowof the at least one first flowable material and the at least one secondflowable material with at least one flow leader in the nonsymmetricalportion of the mold cavity to produce a symmetrical flow boundarydownstream of the nonsymmetrical portion and cause the at least onesecond flowable material to flow throughout substantially the entiremold cavity.

In another aspect, a non-transitory computer readable medium holdscomputer executable instructions for molding a nonsymmetric multiplelayer article. The medium includes instructions for injecting at leastone first flowable material into a mold cavity configured to form amolded article from the at least one first flowable material. The moldcavity comprises a nonsymmetrical portion relative to an injectionlocation of the at least one first flowable material and at least oneflow leader in the non-symmetrical portion. The medium further includesinstructions for co-injecting at least one second flowable material intothe mold cavity and interior to the at least one first flowablematerial. The medium further includes instructions for delaying theco-injection of the at least one second flowable material into the moldcavity after the initial injection of the at least one first flowablematerial by a period of time calculated to produce, in the flow asmodified by the at least one flow leader, a symmetrical flow boundarydownstream of the nonsymmetrical portion and to cause the at least onesecond flowable material to flow throughout substantially the entiremold cavity.

In any of the foregoing aspect, the at least one injection gate may beadjacent to, or remote from, the nonsymmetric portion of the moldcavity.

In any of the foregoing aspects, the at least one flow leader in anon-symmetric portion of the mold cavity may comprise a variablethickness flow leader. The variable thickness flow leader may feature afirst thickness along a first flow path and a second thickness along asecond flow path. The variable thickness flow leader may further feathera smooth transition from the first thickness to the second thickness.The transition may be measured at a single distance from the injectionlocation. Alternatively, the transition may be measured along a firstline that is perpendicular to a second line that intersects theinjection location. In any of the foregoing aspects, the flow leadersmay be configured so that flow fronts of molding material injected intothe flow leaders exit the distal ends of the first and second flow pathsat substantially the same time.

In any of the foregoing aspects, the at least one flow leader maycomprise a plurality of flow leaders defining different thicknessesand/or configurations in a non-symmetric portion of the mold cavity. Theplurality of flow leaders in the nonsymmetrical portion of any of theforegoing aspects may have a flow path length that differs from the flowpath length of adjacent flow leaders by no more than about 15 percent,no more than about 5 percent, or no more than about an intermediatepercentage. In any of the foregoing aspects, the flow leaders may beconfigured so that flow fronts of molding material injected into theflow leaders exit the distal ends of the flow leaders substantiallysimultaneously. In any of the foregoing aspects, the flow leaders may beconfigured so that flow fronts of molding material exit the distal endsof the flow leaders at substantially the same flow rate.

In any of the foregoing aspects, the at least one flow leader may beconfigured so that the velocity of the leading edge of the interiorlayer exiting the distal end of the at least one flow leader issubstantially equal to, and/or greater than, the product of the velocityof the combined flow front multiplied by the quotient of the flowdistance from the leading edge of the interior layer to the periphery ofthe mold divided by the flow distance from the combined flow front tothe periphery of the mold. In any of the foregoing aspects, the at leastone flow leader in the non-symmetrical portion of the mold cavity may beconfigured to produce a symmetrical flow boundary downstream. The flowleader may be configured to produce a uniform or non-uniform symmetricalflow boundary.

In any of the foregoing aspects, the combined flow of the first materialand the second material may be modified in a non-symmetric portion ofthe mold cavity by at least one flow leader. In any of the foregoingaspects, the start of the flow of the second material may be delayed bya time period after the start of the flow of the first material. Thetime period of the delay may be calculated to produce, in the flow asmodified by the at least one flow leader, a symmetrical flow boundarydownstream and to cause the second material to flow throughoutsubstantially the entire mold cavity.

In another aspect, a multiple layer injection molded article comprisesat least one first material generally defining the configuration of themolded article. The molded article includes a non-symmetric portionrelative to an injection location of the first material during injectionmolding. The injection molded article further comprises at least onesecond material substantially contained within the at least one firstmaterial and extending throughout more than 95% of the entire moldedarticle. The length of a path in the non-symmetric portion of the moldedarticle along which the at least one first and the at least one secondmaterials flowed to form the molded article differs from a length of anyadjacent path by no more than about 15%.

In another aspect, a multiple layer injection molded article comprisesat least one first material and at least one second material. The atleast one first material generally defines a configuration of the moldedarticle. The molded article includes a non-symmetric portion relative toan injection location of the first material during injection moldingthereof. The at least one second material is substantially containedwithin the at least one first material and extends throughout more than95 percent of the entire molded article. The non-symmetric portion ofthe molded article features a first thickness with respect to a firstpath and a second thickness with respect to a second path along whichthe at least one first and the at least one second materials flowed toform the molded article. The non-symmetric portion of the molded articlefeatures a smooth transition from the first thickness to the secondthickness.

In another aspect, a multiple layer molded container comprises a closedend defining a periphery thereof and at least one wall extending fromthe periphery of the closed end. The at least one wall defines acontainer sidewall extending completely around the periphery of theclosed end and further defining an open end of the container oppositethe closed end. The closed end and sidewall are formed of first andsecond materials co-injected at an injection location on the closed endand generally defining a configuration of the closed end and thesidewall. The second material is substantially contained within thefirst material. The closed end is nonsymmetrical relative to theinjection location. The open end is enclosable by a substantially gasimpermeable closure to sealingly enclose the container. A length of apath in a non-symmetric portion of the closed end along which the firstand second materials flowed to form the molded container differs from alength of any adjacent path by no more than 15 percent. When thecontainer is sealed by the closure, the oxygen permeation into theenclosed contained is less than about 0.05 ppm per day.

In another aspect, a multiple layer molded container comprises a closedend defining a periphery thereof and at least one wall extending fromthe periphery of the closed end. The at least one wall defines acontainer sidewall extending completely around the periphery of theclosed end and further defines an open end of the container opposite theclosed end. The closed end and the sidewall are formed of first andsecond materials co-injected at an injection location on the closed endand generally define a configuration of the closed end and the sidewall.The second material is substantially contained within the firstmaterial. The closed end is nonsymmetrical relative to the injectionlocation. The open end is enclosable by a substantially gas impermeableclosure to sealingly enclose the container. The non-symmetric portion ofthe closed end features a first thickness with respect to a first pathand a second thickness with respect to a second path along which thefirst and second materials flowed to form the container. Thenon-symmetric portion of the closed end features a smooth transitionfrom the first thickness to the second thickness. When the container issealed by said closure, oxygen permeation into the enclosed container isless than about 0.05 ppm/day.

Portions of any of the foregoing molded articles or containers maycorrespond to the at least one flow leader(s) described above. In any ofthe foregoing molded articles or containers, the second material may befolded over within the first material. When any of the foregoingcontainers is sealed by said closure, oxygen permeation into theenclosed container may be less than about 0.005 ppm/day.

In any of the foregoing aspects, the first material that forms the innerand outer layers may be a different material than the second materialthat forms the interior layer. In any of the foregoing aspects, thefirst material that forms the inner and outer layer(s) may be a plasticmaterial suitable for injection molding, such as polyethylene orpolypropylene. In any of the foregoing aspects, the second material maybe substantially contained or embedded with the inner and outer layers.In any of the foregoing aspects, the second material may be a materialthat is relatively more oxygen impermeable than the first material. Inany of the foregoing aspects, the second material may be a materialand/or compositions exhibiting increased impermeability of gas, light,UV radiation, and/or electromagnetic waves relative to first materialthat forms the inner and outer layer. In any of the foregoing aspects,the second material may include ethyl vinyl alcohol, nylon, an oxygenscavenging material, and/or a desiccant. In any of the foregoingaspects, the interior layer of a co-molded article having anon-symmetrical portion may extend throughout (e.g., between) the innerand outer layers to a greater degree than previously known articles. Inany of the foregoing aspects, the first material and/or the secondmaterial may contain an adhesive.

Exemplary computerized systems, methods and non-transitory computerreadable storage mediums taught herein are configured and adapted tocause the interior core of material to flow in a manner that results inan asymmetric molded plastic article with barrier coverage embeddedwithin greater than 95% of the entire permeation exposed surface area,for example, within the sealed or sealable portion of the article. Thecomputerized systems, methods and non-transitory computer readablestorage mediums taught herein may further be configured and adapted tocause the interior core of material to flow in a manner that results inan asymmetric molded plastic article with barrier coverage embeddedwithin greater than 95% of the entire permeation exposed surface area.In some embodiments, computer readable storage mediums holding computerexecutable instructions are taught. Execution of the instructions by aprocessor controls formation of a co-molded multiple layer article astaught herein. Execution of the instructions by the processor controlsor causes injection of an interior layer material into a combinedmaterial flow in an asymmetric mold cavity having multiple flow leadersthat may have different thicknesses and configurations. The interiorlayer material forms a barrier layer or a scavenger layer in theresulting multiple layer molded article. The exemplary instructions whenexecuted by the processor form the resulting multiple layer moldedarticle with high barrier coverage.

Other objects and advantages of the present invention will becomeapparent in view of the following detailed description of theembodiments and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a prior art injection molded article containinga flow leader.

FIG. 2 is a schematic graph showing oxygen permeation as a function ofbarrier coverage.

FIG. 3A is a perspective view of a container according to an embodimentas taught herein.

FIG. 3B is a schematic cross-sectional view of the container of FIG. 3Aalong the indicated line, but with the wall thickness of the containerexaggerated for illustrative purposes.

FIG. 4 is a schematic cross-sectional view of another containeraccording to an embodiment as taught herein.

FIG. 5A is schematic cross-sectional view of an exemplary material flowin a co-injection molding system according to an embodiment as taughtherein.

FIG. 5B is a schematic cross-sectional view of an exemplary materialflow according to various embodiments taught herein.

FIG. 6A is an illustrative view of an exemplary material flow accordingto various embodiments taught herein.

FIG. 6B is another illustrative view of the exemplary material flow inFIG. 6A according to various embodiments taught herein.

FIG. 7 is a somewhat schematic partial cross-sectional view of thecontainer of FIG. 3A, along the indicated line, but with the wallthickness of container exaggerated for illustrative purposes.

FIG. 8 is an embodiment of a somewhat schematic partial cross-sectionalview of a mold for molding the cross-section shown in FIG. 7.

FIG. 9 is a somewhat schematic partial cross-sectional view of analternative embodiment of a mold.

FIG. 10 is a somewhat schematic partial cross-sectional view of yetanother alternative embodiment of a mold.

FIG. 11 is a plan view of a model for another embodiment of a container.

FIG. 12 is an enlarged view of a prior art flange portion.

FIG. 13 is an enlarged view of the flange portion shown in FIG. 3B.

FIG. 14 is an enlarged view of an alternative embodiment of the flangeportion shown in FIG. 3B.

FIG. 15 is a cross-sectional view of the fountain flow effect of acombined polymeric stream as it flows along an annular pathway of a moldcavity.

FIGS. 16A and 16B are cross-sectional views of the velocity profile ofthe combined annular flow of the polymeric stream and the relativevelocity differences across the flow gradient of the combined polymericstream.

FIG. 17 is a graph illustrating resulting flow fraction and velocityprofile curves across the annular channel within a nozzle.

FIG. 18A is an illustrative view of material flow in a portion of a moldcavity.

FIG. 18B is an illustrative view of material flow in a cross-section ofFIG. 18A.

FIG. 18C is another illustrative view of material flow in the portion ofthe mold cavity illustrated in FIG. 18A.

FIG. 19 is diagram plotting an exemplary volumetric rate of flow ofpolymeric material into a mold cavity versus time.

FIG. 20A is an illustrative view of a portion of a molded part, whichcorresponds to the portion of the mold cavity illustrated in FIG. 18.

FIGS. 20B and 20C are cross-sectional views of the indicated portions ofthe molded part of FIG. 20A.

FIG. 21A is an illustrative view of a portion of a molded part, whichcorresponds to the portion of the mold cavity illustrated in FIG. 18, inaccordance with embodiments taught herein.

FIGS. 21B and 21C are cross-sectional views of the indicated portions ofthe molded part of FIG. 21A, in accordance with embodiments taughtherein.

FIG. 22 depicts a cross-sectional view of an exemplary molding systemaccording to various embodiments taught herein.

FIG. 23 illustrates an exemplary computing environment suitable forpracticing exemplary embodiments taught herein.

DETAILED DESCRIPTION

FIG. 2 schematically illustrates an oxygen permeation curve 50representing oxygen permeation through the walls of a plasticco-injection molded product as a function of coverage of an innerbarrier relative to the total exposed wall surface area of the sealedportion of the product. FIG. 2 also illustrates a target permeation rate60 representing an optimal permeation to prevent undesirable degradationof the substance inside the sealed container. The interior layermaterials associated with the FIG. 2 graph may consist of Ethyl VinylAlcohol (EVOH), MXD6 nylon or other passive barrier materials; EVOH,MXD6 nylon or other barrier materials, any of which has an oxygenscavenging component; or EVOH, MXD6 nylon or other barrier materials,any of which has a desiccant component. As can be seen in FIG. 2, morethan 99% coverage is required to achieve the target permeation rate 60,which, in the illustrated embodiment, is 0.005 ppm O₂/day/container (ppmcalculated on the basis of liquid content of the container). Though thetarget permeation rate 60 may depend upon the particular substance inthe container, the container configuration, and desired storage life (astotal permeation is a function of both rate, exposed area, and time),the inventor considers the depicted target permeation rate 60 to betypical of food-containing articles. Further, while permeation rate isalso dependent upon exposure conditions and to some extent, the wallthickness of the container, one skilled in the food storage arts wouldconsider the permeation curve 50 to be typical of food containers undertypical, if not favorable, storage conditions. Expected variations inthe test parameters produced comparable results.

Depending on the food and the desired storage time (shelf life), thetarget permeation rate 60 may be an order of magnitude higher or lowerthan 0.005 ppm O₂/day/container, i.e., 0.05 or 0.0005 ppmO₂/day/container. The slope of the permeation curve 50 differs withdifferent types and thicknesses of interior layer materials, but oneskilled in the art will appreciate that a significant increase in thepermeation rate occurs with each 1% decrease in the barrier coverage ofthe container surface area.

FIG. 3A depicts a container 100 that achieves the target permeation rateaccording to embodiments taught herein. The container 100 has a bottom105, a sidewall 110 extending from the periphery of the bottom 105 toform a chamber 106, in this embodiment generally cup-shaped or U-shaped,having an open end 107, and a flange 115 extending from the periphery ofthe sidewall 110 at the open end 107 of the container. In theillustrated embodiment, the sidewall 110 has four radiused cornerportions 112 and four straight portions 113 extending between the cornerportions 112. FIG. 3A illustrates corner portions 112 a and 112 b andstraight portions 113 a and 113 b. However, the container 100 may beconfigured as desired for its intended use, having dimensions andstructural integrity adequate for this purpose, e.g., contain thedesired substance. Those skilled in the art will understand how toachieve this.

The container 100 may further include a sealing zone 120 with a sealablesurface. In the embodiment illustrated in FIG. 3A, the sealing zone 120and its surface are formed in the flange 115 and extendcircumferentially about the flange 115. The surface of the sealing zone120 may extend circumferentially throughout substantially the entireflange 115. In the embodiment in FIG. 3A, however, the surface of thesealing zone 120 encompasses only an inner portion of flange 115. Thesealing zone 120 and its surface may be used to engage a removable orunremovable closure (not shown), such as a top or lid, to partially orcompletely enclose the open end 107 of the chamber 106. The closureitself may be substantially gas impermeable. In this manner, the openend 107 of the chamber 106 can be enclosed to both maintain the contentsof the container, e.g., keep fluid substance in the container, andprevent undesirable gas permeation.

The container 100 may be formed by injecting a plastic material, suchas, for example, PET or PP, into a mold cavity so as to form an innerlayer 130 and outer layer 132, which together generally conform to thedesired end shape of the container or product, accounting formanufacturing requirements (e.g., thermal expansion/contraction) as isknown. Despite being termed herein an “inner” or “outer” layer, and inthe illustrated embodiment the inner layer 130 and the outer layer 132form the inside and outside of the container, respectively, it is notintended that those terms be limited in that manner. Rather, the termsmerely refer to the portions of the plastic material that form the wallor “skin” of the molded product. The outer layer 132 and inner layer 130material(s) are injected through an injection gate at location 140, asis known to those in the art. Though PET and PP are commonly usedmaterials, it should be understood that other suitable materials may beused, such as high-density polyethylene (HDPE) or polycarbonates (PC),and that various embodiments can use other polymeric materials.

FIG. 3B shows a cross-section of the container 100 of FIG. 3A along theline indicated in FIG. 3A. However, in FIG. 3B, the wall thickness ofthe container has been exaggerated so as to illustrate the structure. Ascan be seen in FIG. 3B, the container 100 has an interior core layer 150extending substantially entirely throughout the container, but issubstantially fully surrounded by the outer layer 132 and inner layer130. The interior layer 150 is a barrier material, such as EVOH, nylon,MXD6 nylon, an oxygen scavenging material, a desiccant, or othersuitable materials that are known or may become known, that sufficientlyprevents gases, for example, oxygen, from permeating through thecontainer, i.e., from the outside to the inside and vice versa.Similarly, the barrier material of layer 150 may prevent light, UVradiation, and/or electromagnetic waves from permeating through thecontainer. In embodiments with low target gas permeation rates, e.g.,containers for highly oxygen sensitive foods or other materials, theinterior layer 150 may extend along about 99% or more of the exposedsurfaces of the container 100. In some embodiments, the exposed surfacesare those surfaces defined to be within a periphery of a sealing area120. The sealing area 120 is an outer surface, zone, or region to whicha seal contacts to seal the open end 107 of the container. In someembodiments, the exposed surfaces are those surfaces defined to extendbeyond a periphery of a seal contact surface 120.

As shown in FIG. 2, this high coverage by interior layer 150dramatically reduces the gas permeation during typical expected exposureconditions as compared to coverage below 99%. As can be seen in theparticular embodiment of FIG. 3B, the interior layer 150 extends intothe flange 115. In this embodiment, though, as the flange, and thusportion of the interior layer 150 in the flange is at an angle to thesidewall 110 of the container, in this case nearly a right angle, theportion of the interior layer 150 in the flange does not significantlycontribute to the coverage with respect to the exposed area of thecontainer. In other embodiments, depending on the configuration of thecontainer and the flange, the desired degree of coverage, including highdegrees of coverage (e.g., 99% or more), may be obtained without theinterior layer 150 extending into the flange 115 or significantly intothe flange 115. Yet other embodiments may have a flange configurationwherein the flange (or portion thereof) may present an exposed areathrough which gas can permeate into or out of the chamber 106. In suchembodiments, the interior layer 150 may extend into the flange 115 toprovide the desired degree of coverage. Moreover, in embodiments wherethe open end 107 is sealed by a lid or closure, e.g., a heat seal, theinterior layer 150 may not need to extend past the seal to provide anadequate permeation barrier.

By way of example, FIG. 4 depicts another embodiment of a container 100that has a closure 125 closing the open end 107 of the chamber 106. Theclosure 125 itself is typically substantially gas impermeable, e.g., viathe foil material. For example, a commonly known and used lid for usewith food containers is a heat-sealed lid. Such lids may comprise a foillayer, e.g., aluminum foil, with a plastic layer coating on at least aportion of the foil layer that contacts the flange 115 within thesurface area of sealing zone 120. The plastic layer is typically thesame (or similar) material as the container 100. The closure 125 may besealed to the flange 115 at the seal contact surface 120 by conventionalmethods, such as by heat-sealing, crimping, and other known methods.Conventional sealing processes often involves heat and compression,which sufficiently softens and/or melts the plastic layer and/oradjacent flange 115 material to seal the closure to the surface area ofthe sealing zone 120.

As may be noted, the interior layer 150 does not extend to the end ofthe flange. However, those of ordinary skill in the art shouldappreciate that the exposed portion of the flange that does not containthe interior layer is an extremely small portion of overall exposedsurface area of the container 100 (the thickness of the flange 115 inFIG. 4 being greatly exaggerated for illustration purposes). Thus, thedesired degree of coverage, including high degrees of coverage (e.g.,99% or more), may be obtained without the interior layer 150 extendingto the outer periphery of the flange 115, although in some embodimentsthe interior layer may extend to the outer periphery of the flange 115.Put another way, the degree of coverage is most relevant to the sealedor sealable portion of the container 100 that is within the locationwhere the closure 125 is sealed to the container, e.g., the seal contactsurface 120. If an adequate degree of coverage is achieved within thearea defined by the outer bounds of the seal contact surface, zone orregion e.g., 99% coverage within the seal contact surface, desiredpermeation rates may be achieved. In the illustrated embodiment, forexample, the interior layer 150 extends to or beyond the margin of theseal contact surface (in this container configuration the radiallyinward margin), and adequate coverage is obtained without the interiorlayer extending beyond that point. Nonetheless, embodiments also may beutilized to provide the interior layer 150 to or nearly to the end offlange, beyond the seal contact surface margin, as depicted in dashedlines in FIG. 2.

Though the illustrative embodiment has a cup-like shape, the inventioncontemplates containers having alternative shapes or configurations inwhich the sealing zone 120 can be used to seal a portion of thecontainer, which should be appreciated by those in the art. For example,if sidewall 110 had a lip, the lip could alternatively include thesealing zone and its surface. Further, though the embodiment of FIG. 4has an open end 107 that may be closed by a closure 125, alternativeembodiments with different open ends are contemplated. In the embodimentof FIG. 4, the surface area of the sealable portion of the moldedarticle comprises the surface area of the base 105, the surface area ofthe sidewall 110, and the surface area of the portion of the flange 115extending radially under the sealing zone 120 of the closure 125. Thesurface area of the sealable portion of alternative molded articles maybe defined differently depending on their shapes or configurations andwhere they are sealed or intended to be sealed. For example, the surfacearea of the sealable portion of alternative container embodiments maynot extend to a flange, but may instead, for example, extend only to thesealing zone in a lip of the sidewall.

As shown schematically in FIG. 5A, a mold 200 has mold portions 210 a,210 b that form a mold cavity 220 therebetween. Material is injectedfrom a nozzle assembly through an injection gate at gate injectionlocation 140 and into the mold cavity 220. The nozzle assembly forms thecombined flow 300 from the inner material, the outer material, and theinterior material. The combined flow 300, which in certainconfigurations may be an annular flow, flows from the injection location140 through the mold cavity 220. The inner material forms an inner flow,the interior material forms an interior flow 150 a, and the outermaterial forms an outer flow of the combined flow 300. The combined flow300 forms a flow front 330 that moves through the mold cavity 220. Atcertain times, the combined flow 300 may consist of two materials (innerand outer) or three materials (inner, outer, and interior).

An interior material flow is indicated in FIG. 5A as 150 a. An interiorlayer 150 may be created in a molded article by simultaneously injectingthe interior layer material 150 into the interior of the material streamof the outer layer 132 and inner layer 130. Such methods are generallyknown, such as described in U.S. Pat. No. 6,908,581 and the documentsincorporated therein, also incorporated by reference herein in theirentirety.

Similar to FIG. 5A, FIG. 5B schematically shows a mold 200 having moldportions 210 a, 210 b that form a mold cavity 220 therebetween. Asdiscussed in further detail below, the volumetric flow volume ratio ofthe inner flow to the outer flow forming the combined flow 300 may beselected to cause the interior layer flow stream to flow along astreamline offset from the zero velocity gradient 340 (V_(max)) of thecombined flow 300, yet on a streamline having a greater velocity thanthe average flow velocity (V_(ave)) of the combined flow 300. Thisprevents the interior layer material flow 150 a from breaking throughthe flow front 330. Rather, as shown in FIG. 5B, when the leading edgeof the interior layer becomes proximate to the combined stream flowfront 330, the interior layer material flow 150 a folds over to form afoldover portion 150 b behind the flow front 330 and remains encased bythe inner and outer flows of the combined flow 300. By starting theinterior layer material flow 150 a offset from the zero velocitygradient, the interior layer can “catch up” to the flow front forming afountain flow and fold over. This forms a barrier or scavenger layerthat can extend through and provide barrier or scavenger protection overa range of between 99% and 100% coverage through out the resultingmolded plastic article. The interior layer may be located either insideor outside the location of the zero-velocity gradient creating fold overtoward the inside or outside of the part, respectively.

Referring back to FIG. 3A, the bottom 105 of the container is notsymmetric around the injection gate location 140 a. That is, thedistance between the injection gate location 140 a and the periphery ofthe bottom 105 varies around the periphery of the bottom 105. In thisembodiment, this distance is at a minimum along a flow path from theinjection gate location 140 a perpendicular to sidewall straightportions 113 a, increases to a maximum along a flow path perpendicularto the sidewall corner portions 112, and decreases to another minimaalong the flow path perpendicular to sidewall straight portions 113 b.In the embodiment of FIG. 3A, as the container 100 has a generallyrectangular shape, the flow path length from the injection location 140a perpendicular to the sidewall straight portions 113 b is greater thanthe flow path length from the injection location 140 a perpendicular tothe sidewall straight portions 113 a. However, those in the art willunderstand that any non-axially symmetric shape will result in differentflow path lengths.

In order to compensate for the different path lengths, it is known toutilize a mold cavity having a flow leader that consists of a portion ofthe mold cavity with a uniform greater thickness, generally extending inthe directions of the longer flow paths. However, the inventor has foundthat while using such a flow leader is adequate for producing asingle-layer (single material) article, it not does not produce amultiple layer (multiple material) article with sufficient coverage bythe interior layer to prevent undesirable gas permeation. The inventortheorizes that even using such a flow leader, outer layer material flowstransversely to the overall flow direction, impeding the flow ofinterior layer material and preventing adequate formation of theinterior layer. Thus, while known flow leader techniques adequatelycompensate the overall flow of the outer layer material (as in the caseof a mono-material molding), these techniques are inadequate when alsousing an interior layer material in co-injection molding.

The inventor has discovered that a multiple layer article having aninterior layer providing adequate coverage may be molded by using atleast one flow leader in a nonsymmetric portion of a mold cavitydesigned to produce a particular effect on the flow. As used herein withrespect to the invention, the term “flow leader” means a wall portionhaving a thickness different than the nominal design thickness of themold cavity, which is designed to preferentially alter the flow throughthe mold cavity. In some embodiments, a flow leader as taught hereinincludes a wall portion having a varying wall thickness. In someembodiments, a flow leader as taught herein includes a wall portionhaving multiple segments of varying wall thickness. In some embodiments,there may be a relatively smooth transition from a first wall thicknessto a thicker or thinner second wall thickness, for example, a tapered orramped transition. In some embodiments, there may be a relatively abrupttransition from a first wall thickness to a thicker or thinner secondwall thickness, for example, a step transition.

The variable thickness of a flow leader may be selected so that materialinjected into the mold cavity (including both the outer and inner layermaterial and the interior layer material) and passing through the flowleader in the non-symmetric portion of the mold cavity will form a flowboundary downstream of which certain conditions are met. By using avariable thickness flow leader, material flow may be more closelycontrolled and coordinated throughout the mold cavity, permittingimproved and more uniform flow of the interior layer material, forming amore complete interior layer. Additionally or alternatively, thethicknesses of each of a plurality of flow leaders may be selected sothat material injected into the mold cavity (including both the outerand inner layer material and the interior layer material) and passingthrough the plurality of flow leaders in the non-symmetric portion ofthe mold cavity will form a flow boundary downstream of which certainconditions are met. For example, downstream of the flow boundary, theinner and outer layer material and the interior layer material may reachthe periphery of the mold cavity at substantially the same time and,desirably, at substantially the same flow rate (e.g., velocity). Variousembodiments may thus provide co-injected articles with increasedinterior layer coverage than using previously known flow leadertechniques. Embodiments may provide high coverage articles, e.g., withmore than about 99% interior layer coverage.

The thickness of at least one flow leader in a non-symmetric portion ofthe mold cavity may be selected so that material injected into the moldcavity, passing through the at least one flow leader, and existing thedistal end of the flow leader will form a symmetrical flow boundarydownstream in the mold cavity. Similarly, the thickness of each of aplurality of flow leaders in a non-symmetric portion of the mold cavitymay be selected so that material injected into the mold cavity, passingthrough the plurality of flow leaders, and existing the distal end ofthe flow leaders will form a symmetrical flow boundary downstream in themold cavity. The material passing though the symmetrical flow boundarymay reach the periphery of the mold cavity at substantially the sametime and, desirably, at substantially the same flow rate (e.g.,velocity). By using multiple flow leaders, material flow may be moreclosely controlled and coordinated throughout the mold cavity,permitting improved flow of the interior layer material, so that a morecomplete interior layer is formed. Various embodiments may thus provideco-injected articles with increased interior layer coverage than usingpreviously known flow leader techniques. Embodiments may provide highcoverage articles, e.g., with more than about 99% interior layercoverage.

The single or multiple flow leaders as taught herein may be configuredto produce a symmetrical flow boundary downstream. As used with respectto the claims and embodiments taught herein, the term “symmetrical flowboundary” means a boundary downstream of which the velocity of thecombined flow front (V_(F)) is substantially perpendicular to theperiphery of the mold and the velocity of the leading edge of theinterior layer (V_(I)) is substantially equal to, and/or greater than,the product of the velocity of the combined flow front multiplied by thequotient of the flow distance from the leading edge of the interiorlayer to the periphery of the mold divided by the flow distance from thecombined flow front to the periphery of the mold (V_(F)*(L_(I)/L_(F))).

For multilayer flow in accordance with embodiments taught herein, one ormore flow leaders in a non-symmetrical portion of a mold cavity wouldideally be configured to produce a flow boundary in the mold cavitydownstream of which (1) the velocity of the combined flow is effectivelyperpendicular to the periphery of the mold cavity so that the velocityvector has no significant tangential component, and (2) the velocity ofthe leading edge of the interior layer is uniformly proportional to thevelocity of the combined stream flow front around the periphery of themold cavity, such that the leading edge of the interior layer reachesthe desired position proximate to the periphery of the cavity along theentire periphery. This flow boundary is a first example of symmetricalflow boundary. One of ordinary skill in the art will recognize, however,that ideal conditions are rarely fully-achievable under real-worldconstraints.

Accordingly, one of skill in the art will recognize that embodimentstaught herein encompass molds, molding apparatus and methods, moldedarticles, and mediums using at least one flow leader that are configuredto produce less than ideal downstream flow conditions. For example, formultilayer flow in accordance with embodiments taught herein, one ormore flow leaders in a non-symmetrical portion of a mold cavity may beconfigured to produce a flow boundary in the mold cavity downstream ofwhich (1) the velocity of the combined flow is substantiallyperpendicular to the periphery of the mold cavity but the velocityvector has a small tangential component, and/or (2) the velocity of theleading edge of the interior layer is greater than the product of thevelocity of the combined flow front multiplied by the quotient of theflow distance from the leading edge of the interior layer to theperiphery of the mold divided by the flow distance from the combinedflow front to the periphery of the mold, such that at least a portion ofthe leading edge of the interior layer folds over before it reaches thedesired position proximate to the periphery of the cavity. This flowboundary is a second example of symmetrical flow boundary.

As another example, for multilayer flow in accordance with embodimentstaught herein, one or more flow leaders in a non-symmetrical portion ofa mold cavity may be configured to produce a flow boundary in the moldcavity downstream of which (1) the velocity of the combined flow issubstantially perpendicular to the periphery of the mold cavity but thevelocity vector has a small tangential component, and/or (2) thevelocity of the leading edge of the interior layer is substantiallyequal to, but less than, the product of the velocity of the combinedflow front multiplied by the quotient of the flow distance from theleading edge of the interior layer to the periphery of the mold dividedby the flow distance from the combined flow front to the periphery ofthe mold, such that the leading edge of the interior layer reaches thedesired (albeit non-ideal) position proximate to the periphery of thecavity. This flow boundary is a third example of symmetrical flowboundary.

As previously discussed, downstream of a symmetrical flow boundary thevelocity of the combined flow front (V_(F)) is substantiallyperpendicular to the periphery of the mold. For purposes of thisdisclosure, a uniform symmetrical flow boundary is one downstream ofwhich the velocity of the leading edge of the interior layer (V_(I)) iseither substantially equal to or greater than the product of thevelocity of the combined flow front multiplied by the quotient of theflow distance from the leading edge of the interior layer to theperiphery of the mold divided by the flow distance from the combinedflow front to the periphery of the mold (V_(F)*(L_(I)/L_(F))).Downstream of a uniform symmetrical flow boundary, the velocity of theleading edge of the interior layer (V_(I)) is not both substantiallyequal to and greater than the product of the velocity of the combinedflow front multiplied by the quotient of the flow distance from theleading edge of the interior layer to the periphery of the mold dividedby the flow distance from the combined flow front to the periphery ofthe mold (V_(F)*(L_(I)/L_(F)))—in different sections. In contrast,downstream of a non-uniform symmetrical flow boundary, the velocity ofthe leading edge of the interior layer (V_(I)) is both substantiallyequal to and greater than the product of the velocity of the combinedflow front multiplied by the quotient of the flow distance from theleading edge of the interior layer to the periphery of the mold dividedby the flow distance from the combined flow front to the periphery ofthe mold (V_(F)*(L_(I)/L_(F)))—in different sections.

FIG. 6A schematically illustrates material flow in a non-symmetricportion of a mold cavity 220. At least one flow leader (not shown) inthe non-symmetric portion of the cavity 220 creates a symmetrical flowboundary 240 downstream in the cavity. The flow front 330 of thecombined flow 300 moves from the injection location (not shown) throughthe at least one flow leader in the non-symmetric portion of the moldcavity 220 and forms the symmetrical flow boundary 240 downstream of theflow leader(s).

In many cases the flow distance between the symmetrical flow boundary240 and the periphery 250 may be uniform, and such boundaries may bedescribed uniform symmetrical flow boundaries. In FIG. 6A, however, theflow distance 230 a, 230 b, 230 c between the symmetrical flow boundary240 and the periphery 250 of the cavity is not uniform. For example, theflow distance between the symmetrical flow boundary 240 and theperiphery 250 of the cavity in FIG. 6A is greater at the corner 230 athan along the sides as indicated by flow distances 230 b, 230 c.Boundary 240 in FIG. 6A may therefore be described as a non-uniformsymmetrical flow boundary. Whether the boundary is uniform or not, flowsymmetry and interior leading edge symmetry is achieved, under even themost strict definition, when at least one flow leader creates a flowwhereby the quotient of the flow distance (between the boundary and thecavity periphery) divided by the corresponding velocity, for both thecombined and the interior flow, remains approximately equal along theboundary.

Between the symmetrical flow boundary 240 and the mold periphery 250 inFIG. 6A, certain flow conditions are met. For example, the flow in FIG.6A is substantially perpendicular to the cavity periphery 250 betweenthe symmetrical flow boundary 240 and the periphery 250. Moreover, thetangential velocity of the combined flow front 330 in FIG. 6A betweenthe symmetrical flow boundary 240 and the periphery 250 is small, andpreferably effectively zero. FIG. 6A also illustrates the leading edge150 c of the interior layer material flow farther from the periphery 250of the non-symmetric portion of the mold cavity 220 than the flow front330. The distance between the combined flow front 330 and the cavityperiphery 250 is designated in FIG. 6A as the flow distance 370 (L_(F)).The corresponding velocity of the combined flow front is abbreviated asthe flow front velocity (V_(F)). The greater distance between theinterior layer leading edge 150 c and the cavity periphery 250 isdesignated in FIG. 6A as the flow distance 380 (L_(I)). Thecorresponding velocity of the interior layer leading edge is abbreviatedas the interior velocity (V_(I)). FIG. 6B illustrates a cross-section ofFIG. 6A in the indicated position.

When the quotient of the flow distance 370 (L_(F)) divided by the flowfront velocity (V_(F)) is less than the quotient of the flow distance380 (L_(I)) divided by the velocity of the leading edge of the interiorlayer (V_(I)), the flow front 330 reaches the periphery before theleading edge of the interior layer 150 c is proximate to the flow front.Under the foregoing circumstances, the desired coverage of the interiorlayer in molded article may not be attained. If the molded article has awide flange, however, it may not be necessary for the interior layer toreach the periphery of the flange for the desired coverage of theinterior material to be met with respect to the portion of the articleto be sealed.

When the quotient of the flow distance 370 (L_(F)) divided by the flowfront velocity (V_(F)) equals the quotient of the flow distance 380(L_(I)) divided by the interior velocity (V_(I)), the flow front 330 andthe leading edge of the interior layer 150 c reach the periphery 250 atthe same time. One of skill in the art will understand that the leadingedge of the interior layer 150 c preferably reaches the periphery 250 atapproximately the same time as the flow front 330. Thus, idealconditions are met when the foregoing quotients are equal. One of skillin the art will recognize, however, that meeting such conditions alongthe entire periphery 250 of a mold configured to create four or morearticles may not be a practical goal.

One of skill in the art will further understand that foldover of theleading edge of interior layer may be preferable to gaps in theextension of interior layer to the portions of the article to be sealed.When the quotient of the flow distance 370 (L_(F)) divided by the flowfront velocity (V_(F)) is greater than the quotient of the flow distance380 (L_(I)) divided by the interior velocity (V_(I)), the leading edgeof the interior layer 150 c reaches the flow front 330 and fold overoccurs before the flow front 330 reaches the periphery 250. Thus, one ofskill in the art will understand to include at least one flow leaderthat is configured to produce, and possibly a plurality of flow leadersthat together are configured to produce, the relationship between theforegoing quotients associated with the desired result.

Embodiments taught herein provide a molded product with differentthicknesses in a nonsymmetrical portion thereof. Referring again back toFIG. 3A, each of the bottom portions 105 a, 105 b, 105 c, 105 d, 105 e,105 f, 105 g have different thicknesses than an adjacent portion. FIG. 7schematically shows the cross-section of the container 100 of FIG. 3Ataken along the indicated line. Even more so than in FIG. 3A, the wallthickness of the bottom 105 of the container 100 in FIG. 7 has beenexaggerated for illustrative purposes.

FIG. 8 schematically shows a cross-section of a mold 370 forming a moldcavity 375 that may be used to mold the cross-section depicted in FIG.7. The mold cavity 375 thickness is illustratively exaggerated in FIG.8, similar to FIG. 7. The flow leaders 380 a, 380 b, 380 c, 380 d, 380e, 380 f, 380 g have thicknesses selected so that the material flowingthough each flow leader and exiting the distal ends thereof forms asymmetrical flow boundary proximate to the periphery of thenon-symmetrical portion of the mold. The material passing though thesymmetrical flow boundary may then reach the periphery of thenon-symmetric portion of the mold cavity at substantially the same time,with desirably, substantially the same flow rate.

The flow leaders 380 a, 380 b, 380 c, 380 d, 380 e, 380 f, 380 g may beformed in the mold by using known methods to form flow leaders ininjection molds. In the embodiment of FIG. 8, the edge or transition 385between adjacent flow leaders 380 c and 380 d is relatively sharp orsquare. Such transition configurations are conducive to fabrication, assquare edges are nominally formed by many machining processes, e.g.,milling, and do not require additional processing.

Alternatively, as shown in FIG. 9, in the mold 400, which is shown inmagnified view, the square transition 435 (shown in dotted lines)between adjacent flow leaders 430 a, 430 b is processed by suitablemeans, for example, by machining, to provide a contoured, e.g.,radiused, chamfered, rounded, etc., transition 435 a. Such contouredtransitions may involve additional processing to form than sharpertransitions (depending on fabrication method), yet may provide smoothermaterial flow.

As a further alternative, a flow leader may have variable or varyingthicknesses. As illustratively depicted in FIG. 10, in the mold 500, theflow leader 535 (shown in dotted lines) has multiple segments 530 a, 530b, 530 c, 530 d, each of a different thickness. In yet otherembodiments, a flow leader may be configured to have a varying thicknesswithout discrete or sharply defined segments. As also shown in FIG. 10,the flow leader 535 a (shown in a solid line) has a varying thicknesswith smoother contouring than flow leader 535. Such segmenting orcontouring of the flow leader may be achieved by providing the mold withthe desired shape, e.g., by machining. Similarly, referring again toFIG. 9, the transitions between adjacent flow leaders 430 a, 430 b, etc.may be contoured, e.g., by shaping or machining of the mold utilizingthe transitions 435, so that the profile of the mold across the flowleaders is more continuous like flow leader 535 a in the mold shown inFIG. 10.

The configuration (e.g., size and shape) of the flow leaders may dependto significant degree on the configuration of the mold cavity and,ultimately, the configuration of the molded article. Generally, eachflow leader may be configured to direct a portion of the material flowalong its anticipated flow path. This minimizes flow disruptions. Forexample, in the embodiment of FIG. 3A, the bottom 105 of the container100 is generally planar and has a generally uniform thickness (notaccounting for the flow leaders). Accordingly, it is anticipated thatthe bulk flow of the material is generally radially from the injectionlocation 140. Thus, the flow leaders may extend radially from theinjection location 140, having a wedge or pie-shape to form wedge-shapedbottom portions 105 a-105 g. Those in the art should understand,however, that with molded articles (and hence, mold cavities) havingdifferent configurations than shown in FIG. 3A, the anticipated flowpaths may not be radial and the flow leaders may not be pie-shaped.Those of ordinary skill in the art should understand how to shape theflow leaders so as to best conform to the anticipated flow paths.

One need also select the number of flow leaders to be used in the mold.In this regard, a larger number of flow leaders may provide more preciseflow control, and may provide greater interior layer coverage. However,an increased number of flow leaders may require more complicated moldfabrication, e.g., fabricating a large number of separate flow leaders.Further, there may be practical ceilings on the number of flow leadersthat may be provided due to limitations of the fabrication processitself. For example, in embodiments where the flow leaders are machinedinto the mold, the capabilities of the machining equipment may dictate afinite number of flow leaders. Therefore, for ease of fabrication, thesmallest number of flow leaders that can produce the desired coveragemay be used.

As discussed above, disruption to formation of a uniform periphery inthe interior layer may be caused by variations in flow path length inthe mold cavity. The use of multiple flow leaders or at least onevariable-thickness flow leader compensates for this by locally modifyingthe thickness of the mold cavity such that material flow rates and flowtimes through the mold cavity, e.g., in the non-symmetric portion(s),are more consistent. In reality, the material flow path length within aflow leader varies due to the non-symmetric configuration of the mold.Referring to the bottom portion 105 d in FIG. 3A as an example, as itgenerally corresponds to flow leader 380 d (FIG. 8), the flow pathlength along the center of flow leader, i.e., forming the center of thebottom portion 105 d, is longer than the flow paths where the flowleader adjoins flow leaders 380 c and 380 e. This is seen in FIG. 3Awhere the center of bottom portion 105 d is longer than at the edges ofbottom portion 105 d where it adjoins bottom portions 105 c and 105 e.

The epitome of this aspect is demonstrated in previously known singlethickness flow leader configurations, such as shown in FIG. 1. The flowpath lengths 20 a, 20 b and 20 c in flow leader 20 are too different topermit formation of adequate interior layer coverage. By using a largernumber of flow leaders, the flow leaders are smaller, e.g., narrower,and flow path length variation within a flow leader is decreased.

In addition, when using a smaller number of flow leaders, the differenceof flow path length(s) between adjacent flow leaders is greater,resulting in greater variation in flow characteristics between flowleaders. Although flow leader thicknesses assist to compensate for this,if the differences in the flow path lengths are too great, the interiorlayer coverage may not be adequate. Thus, the number, and hence size, offlow leaders may be selected so as to avoid detrimentally large flowlength differences between adjacent flow leaders. The inventor has foundthat when the flow leaders are provided so that flow path lengthsbetween adjacent flow leaders are within about 5%-15%, an adequateinterior layer results. Nonetheless, other variations in flow pathlength may produce adequate coverage and are within the scope of theembodiments taught herein. For example, a single larger flow leaderwhose thickness varies with the flow requirements would also produceadequate interior layer results. For adjacent variable-thickness flowleaders, the difference between the flow path lengths may be quitelarge, on the order of 100% or more, when the variable-thicknessdifferences are sufficient to compensate for the large flow path lengthdifferences. Those of ordinary skill in the art should be able to selectacceptable flow path length variations based on the particularapplication of the various embodiments, for example and withoutlimitation, the configuration of the mold cavity and molded article, themolding process(es) used, the materials utilized, mold fabricationcapabilities, economic considerations, acceptable tolerances for theparticular application, etc.

Once the flow leader configuration is selected, the material flowcharacteristics for each flow leader may be determined. As discussedabove, a significant factor in the formation of an interior layer withadequate coverage is the interior layer leading edge in the flow leadersreaching the periphery of the non-symmetric portion of the mold cavityat substantially the same time, and desirably, at substantially the sameflow rate. The flow time and flow rate at the non-symmetric peripherymay be calculated for each flow leader. This may be accomplished byvarious methods and tools that are known and available to those ofordinary skill in the art, as known mold flow analysis techniques may beutilized. For example, various commercially available software programsare available that will simulate/model the material flow for theselected mold configuration. Suitable computer programs are available,by way of example only, from Moldflow Corporation of Framingham, Mass.Those of ordinary skill will appreciate other suitable computerprograms, that are either currently available or become available in thefuture.

In some embodiments, the pressure drop across each flow leader isutilized. Generally, pressure drop is inversely correlated to flow rate.Table 1 depicts a prophetic example of a molded article having a wallthickness of 0.6 mm (e.g., minimum design thickness), molded utilizing afrozen layer thickness of 10%, providing a nominal flow thickness of0.54 mm.

TABLE 1 Flow Thickness Flow Path ΔP @ Nominal @ Uniform ΔP WallThickness Length Thickness (1614 psi) for Uniform ΔP Segment mm psi mmmm 1 24.4 1614 0.540 0.600 2 25.8 1747 0.564 0.627 3 28.4 2003 0.6090.676 4 32 2364 0.667 0.742 5 35.5 3220 0.792 0.881 6 38.5 3354 0.8110.901 7 40.6 3098 0.776 0.862 8 41.1 2958 0.756 0.840 9 40.6 3692 0.7170.797 10 40.0 2646 0.711 0.790

As shown in Table 1, longer flow paths produce generally higher-pressuredrops that generally correlate to decreases in material flow rates.Adjusting the thicknesses of the flow leaders, e.g., increasing them,thus adjusting the material flow thicknesses, lowers the pressure dropin the flow leaders to a substantially uniform level. In the aboveexample, the flow thicknesses are increased so that the calculatedpressure drops in all flow leaders are substantially equal to the lowestcalculated pressure drop at nominal flow thickness. In this example, thelowest pressure drop at nominal thickness occurs in the flow leader withthe shortest flow path length.

Alternatively, material flow resistance (which can include frictionbetween the injected material and the walls of the mold cavity) may becalculated or measured, e.g., using known methods, and utilized todetermine mold thicknesses that would help balance material flows alongdifferent flow path lengths. Flow resistance is greater along longerflow path lengths. By increasing thickness along a flow path, flowresistance generally decreases. Thicknesses of various flow paths,whether between flow leaders, between segments of a flow leader, orwithin a flow leader of varying thickness, may thus be provided to lowerflow resistance in longer, higher resistance flow paths so that materialflow exits the flow paths at substantially the same time.

In yet other embodiments, the flow leader configurations, e.g.,thicknesses, may be determined experimentally. In such embodiments, thematerial is injected into the mold and the material flow characteristicsare experimentally measured or otherwise determined, using means thatshould be known to those in the art. The experimental results may thenbe used to modify the flow leader configuration, e.g., adjust thethicknesses, the results of which may again be experimentallydetermined. The experimental process may continue until acceptableresults are reached, e.g., substantially consistent material flowcharacteristics.

Further, even when the flow leaders are initially configurednon-experimentally, the configuration may be tested experimentally. Theexperimental results may be used to verify or adjust thenon-experimental modeling results.

Yet further, the coverage of the interior layer in the molded articlemay be experimentally assessed. This may be accomplished in variousmanners as will be appreciated by those of ordinary skill in the art.One such manner, by way of non-limiting example, is to provide theinterior layer material with a different observable characteristic, forexample, color, than the outer layer material. When such a process isused, the coverage of the interior layer within the article, i.e.,within the contrasting outer layer, may be visually assessed. Anothermethod is to assess the gas permeation of the molded article (see FIG.2). While the just-described methods provide various manners ofassessing, those in the art should recognize other suitable methods bywhich to assess the coverage of the interior layer.

Those skilled in the art should also understand that the above-describedmethodologies for configuring the flow leaders are illustrative only.The various embodiments contemplate utilizing any suitable methodologythat is either presently known or will become known. Those of ordinaryskill should appreciate what methodologies are suitable for use with thevarious embodiments.

It should also be noted that in FIG. 3A, the bottom 105 is symmetricabout any axis that passes through the injection location 140 along theplane of the bottom 105. Accordingly, the container 100 is comprised offour substantially identical wedge-shaped quadrants that intersect atthe injection location 140 a. As the quadrants are essentiallygeometrically identical, the flow leaders for the entire container 100may be modeled using only one of the quadrants. In other words, the flowleaders at corresponding locations in the other quadrants may beproduced similarly to those in the modeled quadrant. This avoids theneed to model the entire container, simplifying the modeling process.

An example of this is the container 600 shown in FIG. 11. The container600 is similar to container 100, and therefore like parts are labeledwith similar reference numbers, beginning with “6” instead of “1.”Quadrant 600 a of the container 600 is geometrically identical to theother four quadrants of the container 600 (not shown), i.e., they aremirror images of the quadrant 600 a. Thus, the entire mold for thecontainer 600 may be modeled using the one quadrant 600 a. In thisillustrative embodiment, the model for the quadrant 600 a utilizesthirteen (13) theoretical bottom portions 605 a-605 m, and the mold flowleader thickness corresponding to each theoretical bottom portion may bedetermined in the manner discussed above. The flow leader profile(s)corresponding to the quadrant 600 a may then be used for the remainingthree quadrants of the mold. In this manner, the entire mold may bedesigned based on the quadrant 600 a model. Those skilled in the artwill understand that this methodology may be utilized for any containerthat is “dividable” into two or more substantially identical geometricalsegments. Conversely, this methodology is not applicable if the moldedarticle cannot be “divided” into identical or very similar geometricalsegments.

It should be also noted that merely because the model illustrated inFIG. 11 utilizes thirteen bottom portions does not necessarily mean thatthe corresponding portion of the mold necessarily contains thirteen flowleaders. Various circumstances may dictate or advise a different numberof flow leaders. For example, it may be that the determined thicknessesof adjacent flow leaders are the same, such that the mold may containonly one flow leader instead of two. More specifically, if, by way ofexample only, the theoretical thicknesses of the flow leaderscorresponding to bottom portions 605 h, 605 i, 605 j and 605 k are,respectively, 0.032″, 0.029″, 0.029″, and 0.027″, the mold contains onlyone 0.029″ thick flow leader between flow leaders with thicknesses of0.032″ and 0.027″. In addition, the difference in theoreticalthicknesses between adjacent flow leaders may be so small that it may beunnecessary to provide separate flow leaders. Alternatively, the“combined” flow leader may be provided with the average of thetheoretical thicknesses. Yet further, the obtainable precision andaccuracy of the mold fabrication process may factor. In all suchinstances, it may be desirable to recalculate the flow rates using theadjusted thicknesses to ensure any flow variance caused by the deviationfrom the theoretical thicknesses are not significant enough to impactthe permeability of the article, e.g., barrier coverage.

In both the embodiments shown in FIG. 3A and FIG. 11, the flow pathlengths along the sidewall 110, 610 are substantially equal because thesidewall has a consistent contour and height around the circumference ofthe container. Thus, if the flow streams of the interior layer 150reaches the portion of the mold cavity that forms the sidewall 110, 610after passing through a symmetrical flow boundary, the flow front ofinterior layer material 150 advances along the sidewall portion of themold with the desired flow characteristics and forms a comprehensiveinterior layer 150. Moreover, if the flange 115 has a consistent widthas in the embodiment of FIG. 3A, the interior layer material 150advances with the desired flow characteristics along the flange-formingportion of the mold cavity and forms a comprehensive interior layer 150in the flange 115. Similarly, if the flow streams of the interior layer150 reaches the portion of the mold cavity that forms the sidewall 110,610 at the same time and with the same flow rate, the flow front ofinterior layer material 150 advances consistently along the sidewallportion of the mold and form a consistent interior layer 150. Moreover,if the flange 115 has a consistent width as in the embodiment of FIG.3A, the interior layer material 150 advances consistently along theflange-forming portion of the mold cavity to form a consistent interiorlayer 150 in the flange 115. As noted above, though, in some embodimentsthe formation of an interior layer 150 in the flange, particularlytoward the end of the flange 115, may not significantly affectpermeation.

If, on the other hand, the container sidewall does not have a consistentcontour or configuration, the flow path lengths at different locationsof the sidewall will differ. This may curtail adequate interior layer150 formation in the sidewall (and the flange 115) in such instances,the principles of the invention as described above may also be appliedto the sidewall-forming portions of the mold. Similarly, in theembodiment of FIG. 11, the flange 615 has areas of increased width,resulting in increased flow path length. Again, if necessary or desired,the various embodiments may be implemented to compensate for thedifferent flow path lengths.

Yet further, in the embodiment of FIG. 11, the sidewall 610 is notoriented at a right angle to the bottom 605, but continues to expandradially outward, i.e., the container cavity 606 “widens” toward theopen end 607. Though the flow path length is still consistent, the areaof the sidewall increases in the corner portions 612 toward the open end607. As the area increases, the volume of material needed to form thecorner portions is greater than that required for the straight portions613 a, 613 b. Accordingly, the flow leaders feeding material to thecorner portions 612 may be adjusted to provide the greater volumetricflow rate needed to provide consistent advancement of the interior layermaterial 150 flow front. A similar situation exists in the areas of theflanges 115, 615 adjacent the corner portions 112, 612 as they tooincrease in area extending from the top of the sidewall 110, 610 atthese locations. Similar compensatory adjustments may be made.

In addition, as shown in FIG. 1, the container 100 has one (1) injectiongate location 15. This is typical with containers such as shown in FIG.1, as it often presents the simplest manufacturing process. It should beunderstood, of course, that the flow leader embodiments taught hereinare not limited to containers molded using a single gate, and the flowleader embodiments taught herein contemplate and are applicable to theuse of multiple injection gates, as may be desired or preferreddepending on the particular article to be molded, the complexity of themold, and other factors that will be understood by those of ordinaryskill in the art.

It should also be understood that practical application processvariations may exist by which the flow of the interior layer materialmay vary from the calculated flow characteristics. Such processvariations may include, by way of example only, manufacturing tolerancesin mold cavity dimensions and surface finishes, local temperaturevariations, injection pressure variations, normally occurring streamlinevariations, limitations of calculation methodologies used, lot-to-lotvariation of the properties of the inner, outer, and/or interior layermaterial, etc. that will be understood by those of ordinary skill in theart. As an example, as shown in FIG. 12, process variations can preventthe interior layer 150 from reaching the periphery 250 of the moldcavity, which leaves an unprotected portion 133 on the outer layer 132and inner layer 130 through which gas 137 may permeate. This may occur,by way of example referring to FIG. 12, when the interior layer material150 lags the flow front, and thus the flow front reaches the end 250 ofthe mold cavity (the end of flange 115) before the interior layermaterial 150 reaches the flange.

However, the inventor has found that when the various flow leaderembodiments were implemented, these process variations do notsignificantly disrupt the formation of a high coverage barrier layer, orcan be iteratively adjusted to obtain a desired barrier coverage. Thus,a high coverage interior layer 150 may be obtained as shown in FIG. 13.

The flow leader technology and related molds, apparatuses, and methodsof the embodiments taught herein may be used alone, or as discussedabove, in conjunction with fold over or wrapping of the interior layerto form a multiple layer molded article. Various embodiments may thusutilize fold over, e.g., the methods and apparatuses disclosed in U.S.Pat. No. 6,908,581, which is hereby incorporated by reference in itsentirety, to prevent breakthrough of the interior layer material throughthe flow front of the combined layer flow. Referring again to FIG. 5A,the injection is performed so that the flow of the interior layermaterial 150 is offset from the zero velocity gradient 340 (V_(max)) ofthe material flow, yet on a streamline having a greater velocity thanthe average flow velocity (V_(ave)). As depicted in FIG. 14, thisprevents the interior layer material 150 from breaking through the flowfront 330. Rather, the interior layer material 150 folds over andremains within the outer layer 132 and inner layer 130.

These foldover processes may also be utilized to adjust for theabove-mentioned process variations, particularly for high outputproduction systems having multiple mold cavities. For example, one wayto adjust for incomplete coverage as shown in FIG. 12 is to control theinjection parameters of the interior layer material 150 (e.g., injectiontiming, location, pressure, etc.) so that the interior layer material150 does not lag behind the combined flow front. However, as discussedin the aforementioned U.S. Pat. No. 6,908,581, this can cause theinterior layer material 150 to break through the flow front. Conversely,if breakthrough is occurring, the parameters can be adjusted so that theinterior layer material 150 does not catch up to the flow front. This,though, can cause incomplete coverage, e.g., as in FIG. 12.

Implementation of a foldover process can mitigate these issues. Using afoldover process, the injection parameters can be controlled so thatinterior layer material 150 reaches the end of the mold cavitysubstantially throughout the molded article without breakthroughconcern. Additional interior layer material 150 simply continues to foldover behind the flow front to the degree necessary to accommodate thesurplus interior layer material 150, which may occur in portions or allof any one cavity or cavities in a multi-cavity production system.

In embodiments where a heat seal may be utilized, a fold over processmay be used as described in commonly owned U.S. Patent Application Ser.No. 61/416,903, entitled “HEAT-SEAL FAILURE PREVENTION METHOD andARTICLE” and filed Nov. 24, 2010, which is incorporated by referenceherein in its entirety. As described therein, and as depicted in FIG.14, the interior layer 150 can be offset to the side of the outer layer132 that is opposite from the surface of the flange 115 that forms theheat seal. In this manner, the foldover portion 150 a does not interferewith the structural integrity of the heat seal.

It should be noted that in such embodiments where a lid or other closureis heat sealed to the container 100, the heat seal itself does notcontain the interior layer 150. However, the heat seal itself istypically very thin, particularly in relation to its length. Further, inembodiments where the lid is sealed to the flange 115, the total exposedsurface area between the interior layer 150 and the heat seal lid isvery small, especially in comparison with the container itself, and gaspermeation though the heat seal area is not significant.

FIGS. 15 through 16A-B illustrate material flow properties, which may beleveraged in conjunction with flow leader technology disclosed herein toproduce fold over in the interior layer as needed to attain the desiredcoverage. FIG. 15 depicts the fountain flow effects whereby flowingmaterial upstream of the flow-front 23 has a velocity profile 350(V_(P)) such that the volumetric flow rate is fastest in the middle andslowest at or near the interface of the polymeric stream and the wallsof the channels of the mold cavity.

FIGS. 16A and 16B depicts the velocity profile 350 (V_(P)), where thecombined stream is fastest at point “A” and slower at points “B” and“C”. The zero-velocity gradient 340 occurs at the point where thevelocity of the flow is greatest. Because the flow at the zero-velocitygradient streamline is greater than the average velocity of theflow-front, the interior material injected at or near the zero velocitygradient point can, under some circumstances “catch up” to and pass theflow-front and break through the skin, even if injection of the interiormaterial begins after injection of the inner and outer layers (PET, PC,HDPE, or PP). The interior core stream material breaks through after theinterior material reaches the flow-front of the combined polymericstream.

FIG. 16B shows that as the particles initially at points A, B, and Crespectively move downstream, they move farther apart from each otherdue to velocity profile 350. After a first period of time elapses, theparticles will have moved to new locations designated as A₁, B₁, and C₁respectively. After a second period of time elapses, the particles willhave moved to new locations designated as A₂, B₂, and C₂ respectively.The relative location of the particles at the successive timesdemonstrates the effect of the velocity profile 350 over time. Sinceflow velocity at point A is greater than the velocity at point B, theparticle starting at point A will move farther over time than theparticle starting at point B. Similarly, since flow velocity at point Bis greater than the velocity at point C, the particle starting at pointB will move farther over time than the particle starting at point C.

FIG. 17 plots the ratio of flow velocity-to-average flow velocity as afunction of the radius of the annulus between the inner and outer flowchannel walls. FIG. 17 depicts the normalized velocity profile 350 andvolume fraction inside and outside for a fluid with n=0.8 (where n isthe parameter for the non-Newtonian power law model of fluid flow). Thezero gradient 340 for the combined flow stream (CF) is marked on thenormalize velocity profile 350. The curve designated with a circlemarker plots the inner flow (IF) between the radius and the innercylindrical wall T from the inner to the outer wall. The curve markedwith a triangle plots the outer flow (OF) between the outer cylindricalwall and the annular radius. The hatched area shows the acceptablelocation for interior layer placement that is both greater than theaverage velocity and off the zero velocity gradient 340. The interiorlayer material placed within this area will wrap to the inside of thepart. From the graph we can see that the flow fraction of the insidelayer can be in a range from 0.1 to 0.45. The flow fraction of theoutside layer can be from 0.9 to 0.55. The interior layer thickness canbe as thick as about 25% of the thickness of the flowing layer which isabout 35% of the flow fraction, 0.1 to 0.45. If the hatched area were onthe opposite side of the zero velocity gradient 340, the flow fractionof the inside layer and outside layer would be of similar magnitude, butinversed.

FIGS. 18A through 21C illustrate imperfect flow, such as may be producedby an imperfect flow leader, and the potential effect of a timingadjustment on the product of that flow. FIGS. 18A and 18C illustrate asegment of a mold cavity chosen to illustrate imperfect flow within thecavity. FIGS. 18A and 18B illustrate conditions that cause tangentialflow at the flow front 330. FIG. 18C illustrates the effect oftangential flow on the interior layer leading edge 150 c. In FIGS. 18Aand 18C, the combined flow 300 begins as material is injected at aninjection gate at location 140 and moves toward the periphery 250 of amold cavity. In FIGS. 18A and 18C, the combined flow 300 is divided intothe same three segments 300 a, 300 b, and 300 c. The flow front 330 ofthe combined flow 300 is illustrated in FIGS. 18A, 18B, and 18C as itmoves toward the periphery 250 of the mold cavity in a direction that issubstantially perpendicular to the periphery 250.

As illustrated in FIG. 18A, the velocity of the flow front (V_(F)) ineach segment is approximately equal. The velocities of the flow front insegments 300 a and 300 c (V_(Fa) and V_(Fc), respectively) have a smalltangential component direct toward middle segment 300 b. As illustratedin FIG. 18A, the small tangential component of the velocity of the flowfront in segment 300 a (V_(Ta)) causes material from the combined flowin segment 300 a to flow into the combined flow in segment 300 b.Similarly, the small tangential component of the velocity of the flowfront in segment 300 c (V_(Tc)) causes material from the combined flowin segment 300 c to flow into the combined flow in segment 300 b.

FIG. 18B is a cross-sectional illustration of the flow in a segment ofthe cavity illustrated in FIG. 18A. FIG. 18B illustrates the fountainflow effect that occurs at the flow front 330. FIG. 18B furtherillustrates the centerline velocity (V_(C)), which may be the zerogradient velocity. A centerline velocity V_(C) in one segment of thecombined flow 300 that is greater than the centerline velocity V_(C) inan adjacent segment creates a tangential component in the flow frontvelocity V_(T) in the faster flowing segment.

FIG. 18B specifically illustrates a cross-section of the flow in segment300 c of FIG. 18A. A centerline velocity in segment 300 c (V_(Cc)) thatis greater than the centerline velocity in segment 300 b (V_(Cb))creates the tangential component in the flow front velocity in segment300 c (V_(Tc)) directed toward segment 300 b as illustrated in FIG. 18A.A cross-sectional illustration of the combined flow in segment 300 awould be similar to FIG. 18B. And a centerline velocity in segment 300 a(V_(Ca)) that is greater than the centerline velocity in segment 300 b(V_(Cb)) similarly creates a tangential component in the flow frontvelocity in segment 300 a (V_(Ta)) directed toward segment 300 b asillustrated in FIG. 18A.

FIG. 18C illustrates the interior layer leading edge 150 c within thecombined flow 300. In particular, FIG. 18C illustrates that the interiorlayer leading edge 150 c lagging behind the flow front 330 in segment300 b, particularly in comparison to the position of the interior layerleading edge 150 c with respect to the flow front 330 in segments 300 aand 300 c. The interior layer leading edge 150 c lags in segment 300 bdue to the tangential flow components of the flow front velocity V_(T)in segments 300 a and 300 c. FIG. 18C illustrates a flow boundary thatis not a symmetrical flow boundary.

Returning to FIG. 18B, we note that FIG. 18B further illustrates theinterior layer leading edge 150 c in combined flow 300. The interiorlayer leading edge 150 c has its own velocity (V_(I)). The ratio of theflow front velocity V_(F) over the leading edge velocity V_(I) isdetermined by the offset of the interior layer from the flow centerline.Accordingly, the offset of the interior layer from the flow centerlinecan be selected to get the desired ratio V_(F)/V_(I). For example, wherethe leading edge velocity V_(I) is approximately equal to the centerlinevelocity V_(C) and the centerline velocity V_(C) is approximately 1.3times the flow front velocity V_(F), the ratio V_(F)/V_(I) is about 1divided by 1.3, or about 0.769. Increasing the offset of the interiorlayer from the flow centerline generally decreases the leading edgevelocity V_(I) and therefore generally increases the ratio V_(F)/V_(I).

FIG. 19 illustrates an exemplary plot of the volumetric flow of apolymeric stream into a mold cavity over time. The horizontal axis ofFIG. 19 represents time, and the vertical axis of FIG. 19 represents thevolumetric material flow rate. The time line of FIG. 19 begins with theflow of polymer into the mold cavity. Curve 1710 illustrates thevolumetric flow rate of the sum of the inner and outer layer polymer.The flow initially increases quickly, as illustrated by curve 1710. Theinner and outer layer polymer forms the inner and outer layers of amolded article. In FIG. 19, an interior layer polymer is added to theflow into the mold cavity after 0.1 second as illustrated by curve 1720.The interior layer polymer forms the interior layer of the moldedarticle. The delay between the initial flow of the inner and outer layerpolymer and the initial flow of the interior layer polymer is designatedas time delay d 1730. The time delay d differs in various embodimentstaught herein.

Returning to FIG. 18B, we again note that FIG. 18B illustrates theinterior layer leading edge 150 c in combined flow 300. As in FIGS.6A-B, the distance between the combined flow front 330 and the cavityperiphery 250 is designated in FIG. 18B as the flow distance 370(L_(F)). Also as in FIGS. 6A-B, the greater distance between theinterior layer leading edge 150 c and the cavity periphery 250 isdesignated in FIG. 18B as the flow distance 380 (L_(I)). The ratio ofdistance 370 over distance 380 (L_(F)/L_(I)) is determined by the timedelay d in adding the interior layer material to the polymeric streaminjected into the mold cavity.

If the flow boundary is uniform in all cavities of a molding system,then a time delay d of approximately 0.1 second enables the interiorlayer leading edge to flow proximate to the periphery of the molded partin all cavities. For the example described above with respect to FIG.18B, in which the ratio V_(F)/V_(I) is about 0.769, the ratio ofdistance 370 over distance 380 (L_(F)/L_(I)) is the “ideal” proportionfor the given interior layer offset when time delay d 1730 isapproximately 0.1 second and the time for the flow front to reach thepart periphery is slightly less than 0.4 second as illustrated in FIG.19—that is the ratio of distance 370 over the flow front velocity isequal to the ratio of distance 380 over the leading edge velocity (i.e.,(L_(F)/V_(F))=(L_(I)/V_(I))). Stated an another way, the velocity of theleading edge of the interior layer is equal to the product of thevelocity of the combined flow front multiplied by the quotient of theflow distance from the leading edge of the interior layer to theperiphery of the mold divided by the flow distance from the combinedflow front to the periphery of the mold (i.e.,V_(I)=V_(F)*(L_(I)/L_(F))). In the ideal case, the flow front of thecombined flow reaches the periphery of the mold cavity just as theleading edge of the interior layer becomes proximate to the flow front.

If the flow boundary is not uniformly the same in any one cavity asillustrated in FIG. 18C or between cavities in a multi-cavity moldingsystem, then setting a time delay d to less than 0.1 second createsfoldover in the portion(s) of the molded part(s) in which the ratioL_(F)/L_(I) is larger than the “ideal” proportion. The ratio of distance370 over distance 380 (L_(F)/L_(I)) is larger if the time delay d isless than 0.1 second. When the ratio L_(F)/L_(I) is larger, the flowfront 300 reaches the periphery 250 after the leading edge of theinterior layer 150 c becomes proximate to the flow front 330 and foldsover. In sum, the larger ratio L_(F)/L_(I), which can be caused by asmaller time delay d, makes fold over more likely to occur. Asdescribed, a flow boundary that is not symmetrical may be made to be anon-uniform symmetrical flow boundary by appropriately decreasing timedelay d.

On the other hand, setting a time delay d to greater than 0.1 seconddecreases the ratio of distance 370 over distance 380 (L_(F)/L_(I)).When the ratio L_(F)/L_(I) is smaller, the flow front 300 reaches theperiphery 250 before the leading edge of the interior layer 150 cbecomes proximate to the flow front 330—potentially leaving anundesirable gap in the coverage of the interior layer 150 within in theresulting molded article.

FIGS. 20A-C and FIGS. 21A-C illustrate the same portion of alternativemolded parts that may result from different flow conditions in the moldcavity illustrated in FIGS. 18A and 18C. The periphery of the moldedparts in FIGS. 20 and 21 correspond to the periphery 250 of the moldcavity in FIGS. 18A-C; accordingly, the periphery of the molded partsare similarly designated 250. The material injection location of themolded parts in FIGS. 20A and 21A similarly correspond to the injectionlocation 140 of the mold cavity in FIGS. 18A and 18C; accordingly, theinjection location of the molded parts are similarly designated 140.FIGS. 20A and 21A are each divided into three segments 132 a, 132 b, 132c, which correspond to the combined flow segments 300 a, 300 b, and 300c of FIG. 18A, respectively.

FIGS. 20A-C illustrate the leading edge 150 c of the interior layer in aportion of a molded part 101 created with a time delay d ofapproximately 0.1 second. The flow boundary created in the production ofmolded part 101, however, is not uniformly the same in any one cavity orbetween cavities of the molding system. Thus, the leading edge 150 c ofthe interior layer in FIG. 20A is much farther from the periphery 250 insegment 132 b than in segments 132 a and 132 c. FIG. 20B illustrates across-sectional view of segment 132 b of FIG. 20A. FIG. 20C illustratesa cross-sectional view of segment 132 a of FIG. 20A. A cross-sectionalview of segment 132 c of FIG. 20A would be similar to FIG. 20C, anddifferent than FIG. 20B. A comparison of the distance between theleading edge 150 c and the periphery 250 in FIG. 20B to thecorresponding distance in FIG. 20C confirms that the leading edge 150 cis much farther from the periphery 250 in segment 132 b than in segments132 a (or 132 c).

FIGS. 21A-C illustrate the interior layer 150 in a portion of a moldedpart 100 produced in the same molding system as FIGS. 20A-C, but with atime delay d of less than 0.1 second sufficiently to produce anon-uniform symmetrical flow boundary. Unlike the interior layer insegment 132 b of FIG. 20A, the interior layer 150 in segment 132 b ofFIG. 21A is proximate to the periphery of the molded part. As in FIG.20A, the interior layer leading edge 150 c in segment 132 b laggedbehind the leading edges 150 c in segments 132 a and 132 c during theproduction of FIG. 21A's molded part 100. The advanced portions of theinterior layer leading edge 150 c became proximate to flow front 330earlier, however, and folded over to create foldover portions 150 b insegments 132 a and 132 c.

FIG. 21B illustrates a cross-sectional view of segment 132 b of FIG.21A. FIG. 21B illustrates the interior layer 150 having a small foldoverportion 150 b in segment 132 b. Other embodiments taught herein,however, include no foldover portion of the interior layer 150 in thelagging segment. FIG. 21C illustrates a cross-sectional view of segment132 a of FIG. 21A. A cross-sectional view of segment 132 c of FIG. 21Awould be similar to FIG. 21C, but different than FIG. 21B. FIG. 21Cillustrates a segment of molded part 100 in which the interior layerleading edge 150 c reached the flow front 330 and created a foldoverportion 150 b during production large enough to allow the laggingportion of leading edge 150 c in segment 132 b to become proximate tothe periphery. FIGS. 21A-C illustrate the effect of adjusting the timedelay to create foldover when it is necessary to use foldover to correctfor imperfect flow.

FIGS. 21A-C further illustrate some embodiments in which a time delayadjustment is used in conjunction with a flow leader to create asymmetrical flow boundary that will provide the desired coverage of theinterior layer in the resulting molded product. One skilled in the artknows it is difficult to create a perfect flow leader for manynon-symmetric molded parts, and can appreciate that techniques may beused to achieve the necessary coverage of the interior layer.

FIG. 22 illustrates an exemplary system suitable for practicingexemplary embodiments. Co-injection molding system 1000 is configured toinject at least two materials into a mold cavity. Materials suitable foruse include all materials previously discussed. Co-injection moldingsystem 1000 includes a first material source 1200, a second materialsource 1400, and a manifold 1600. Manifold 1600 may consist of separatemanifolds for each polymeric material. Co-injection molding system 1000further includes nozzle assemblies 18A, 18B, 18C, 18D and mold 2400.Mold 2400 includes gates 2420A, 2420B, 2420C, 2420D, and cavities 2422A,2422B, 2422C, 2422D. In FIG. 22, each nozzle assembly 18 corresponds toa gate 2420 and a cavity 2422. For example, nozzle assembly 18Acorresponds to gate 2420A and cavity 2422A. One of skill in the art willunderstand that although four mold cavities are illustrated in FIG. 22,mold 2400 may include a different number of mold cavities. For example,mold 2400 may include any number of mold cavities up to 64 or more moldcavities. In one embodiment, each cavity in mold 2400 forms a separatemolded article.

A first polymeric material is extruded from the first material source1200 and a second polymeric material is extruded from the secondmaterial source 1400 into the manifold 1600 for combining in nozzles18A, 18B, 18C, 18D before being injected into mold cavities 2422A,2422B, 2422C, 2422D. The first and second polymeric streams are combinedto form an annular combined polymeric stream such that the firstpolymeric material forms an interior core stream in the combinedpolymeric stream while the second polymeric material forms the inner andouter streams in the combined stream. The inner and outer streams encasethe interior core stream as the annular combined polymeric stream isinjected from the nozzle.

In alternative embodiment (not shown), molding system 1000 is configuredto form a plurality of open containers that are connected to each other.In this embodiment, mold 2400 is configured to form a molded articlecomprising a plurality of open containers. For example, the moldedarticle may include 4, 6, 8, or more open containers. In such anembodiment, there need not be a nozzle assembly or injection gatededicated to forming each container. Instead, a single nozzle assemblyand injection gate may form a plurality of connected molded containers.The connected containers may be used as a plurality of connectedcontainers. Alternatively, the connected containers may be separated andthen used.

FIG. 23 illustrates an exemplary computing environment suitable forpracticing exemplary embodiments taught herein. The environment mayinclude a co-injection control device 900 coupled, wired, wirelessly ora hybrid of wired and wirelessly, to co-injection system 1000. Theco-injection control device 900 is programmable to implement executableBarrier Coverage Code 950 for forming a barrier layer or scavenger layerthat provides coverage over a range of between 95% and 100%, or evenbetween 99% and 100%, of a sealed or sealable portion of non-symmetriccontainer or a sealable portion of a non-symmetric cap surface area astaught herein. Co-injection control device 900 includes one or morecomputer-readable media for storing one or more computer-executableinstructions or software for implementing exemplary embodiments. Thecomputer-readable media may include, but are not limited to, one or moretypes of hardware memory, non-transitory tangible media, etc. Forexample, memory 906 included in the co-injection control device 900 maystore computer-executable instructions or software, e.g., instructionsfor implementing and executing the executable Barrier Coverage Code 950.Co-injection control device 900 also includes processor 902 and, one ormore processor(s) 902′ for executing software stored in the memory 906,and other programs for controlling system hardware. Processor 902 andprocessor(s) 902′ each can be a single core processor or multiple core(904 and 904′) processor.

Virtualization may be employed in co-injection control device 900 sothat infrastructure and resources in the computing device can be shareddynamically. Virtualized processors may also be used with the executableBarrier Coverage Code 950 and other software in storage 916. A virtualmachine 914 may be provided to handle a process running on multipleprocessors so that the process appears to be using only one computingresource rather than multiple. Multiple virtual machines can also beused with one processor.

Memory 906 may comprise a computer system memory or random accessmemory, such as DRAM, SRAM, EDO RAM, etc. Memory 906 may comprise othertypes of memory as well, or combinations thereof.

A user may interact with co-injection control device 900 through avisual display device 922, such as a computer monitor, which may displaythe user interfaces 924 or any other interface. The visual displaydevice 922 may also display other aspects or elements of exemplaryembodiments, e.g. the databases, etc. Co-injection control device 900may include other I/O devices such a keyboard or a multiple point touchinterface 908 and a pointing device 910, for example a mouse, forreceiving input from a user. The keyboard 908 and the pointing device910 may be connected to the visual display device 922. Co-injectioncontrol device 900 may include other suitable conventional I/Operipherals. Co-injection control device 900 may further comprise astorage device 916, such as a hard-drive, CD-ROM, or othernon-transitory computer readable media, for storing an operating system918 and other related software, and for storing executable BarrierCoverage Code 950.

Co-injection control device 900 may include a network interface 912 tointerface to a Local Area Network (LAN), Wide Area Network (WAN) or theInternet through a variety of connections including, but not limited to,standard telephone lines, LAN or WAN links (e.g., 802.11, T1, T3, 56 kb,X.25), broadband connections (e.g., ISDN, Frame Relay, ATM), wirelessconnections, controller area network (CAN), or some combination of anyor all of the above. The network interface 912 may comprise a built-innetwork adapter, network interface card, PCMCIA network card, card busnetwork adapter, wireless network adapter, USB network adapter, modem orany other device suitable for interfacing authorization computing device900 to any type of network capable of communication and performing theoperations described herein. Moreover, co-injection control device 900may be any computer system such as a workstation, desktop computer,server, laptop, handheld computer or other form of computing ortelecommunications device that is capable of communication and that hassufficient processor power and memory capacity to perform the operationsdescribed herein.

Co-injection control device 900 can be running any operating system suchas any of the versions of the Microsoft® Windows® operating systems, thedifferent releases of the Unix and Linux operating systems, any versionof the MacOS® for Macintosh computers, any embedded operating system,any real-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices, or any other operating system capable of running on thecomputing device and performing the operations described herein. Theoperating system may be running in native mode or emulated mode.

Barrier Coverage Code 950 includes executable code executable by theprocessor 902 to control the co-injection system 1000 to selectivelycontrol a volumetric flow volume of the inner and outer polymericstreams, control a position of the interior core material stream 150 arelative to a velocity flow front of the combined polymeric stream andcontrol extrusion start time of the interior core stream relative to theextrusion start time of the inner and outer polymeric streams as taughtherein. That is, Barrier Coverage Code 950 includes executable codeexecutable by the processor 902 to control the co-injection system 1000to place the interior core material flow stream 150 a on a flowstreamline that has a velocity that is greater that the average velocityof the combined annular flow 300. Thus, the interior layer material flow150 a can “catch up” to the fountain flow and fold over, creatingcoverage of a barrier layer or scavenger layer in the resulting moldedarticle in a range of between 99% and 100% coverage in a sealable orsealed area of the article. Execution of the Barrier Coverage Code 950by the processor 902 allows the co-injection system 1000 to place theinterior layer material flow 150 a either inside or outside the locationof the zero-velocity gradient creating fold over toward the inside oroutside of the resulting article, respectively. Methods and co-injectionsystems taught herein facilitate the co-injection molding ofnon-symmetrical food or beverage containers whereby the interior layerextends between 99% and 100% of a sealable or sealed area formed by thewalls, flange and closed end of the resulting molded container. Thesealable or sealed area is defined by an interior portion of theresulting molded article that extends to a surface of a sealing area120, which may be located in a flange portion of the resulting moldedarticle.

As may be recognized by those of ordinary skill in the pertinent artbased on the teachings herein, numerous changes and modifications may bemade to the above-described and other embodiments of the presentdisclosure without departing from the spirit of the invention as definedin the appended claims. Accordingly, this detailed description ofembodiments is to be taken in an illustrative, as opposed to a limiting,sense.

Although the claims recite specific combinations of limitations, theinvention expressly encompasses each independent claim by itself andalso in conjunction with any possible combination of limitationsarticulated in the related dependent claims except those that areclearly incompatible.

1.-29. (canceled)
 30. A multiple layer injection molded articlecomprising: (a) at least one first material generally defining aconfiguration of the molded article, the molded article comprising anon-symmetric portion relative to an injection location of the firstmaterial during injection molding thereof; and (b) at least one secondmaterial substantially contained within the at least one first materialand extending throughout more than 95 percent of the entire moldedarticle; wherein a length of a path in the non-symmetric portion alongwhich the at least one first and the at least one second materialsflowed to form the molded article differs from a length of any adjacentpath by no more than about 15%.
 31. The multiple layer injection moldedarticle of claim 30 wherein the at least one first material comprises aplastic material including at least one of polyethylene andpolypropylene.
 32. The multiple layer injection molded article of claim30 wherein the at least one first material and at least one secondmaterial comprise different materials.
 33. The multiple layer injectionmolded article of claim 30 wherein the at least one second material isrelatively more gas impermeable than the at least one first material.34. The multiple layer injection molded article of claim 30 wherein theat least one second material comprises at least one of ethyl vinylalcohol, nylon, an oxygen scavenging material, and a desiccant.
 35. Themultiple layer injection molded article of claim 30 wherein one of theat least one first material and the at least one second materialcomprises an adhesive.
 36. The multiple layer injection molded articleof claim 30 wherein the at least one second material extends throughoutat least about 99% of the molded article.
 37. The multiple layerinjection molded article of claim 30 wherein at least a portion of theat least one second material is folded over within the at least onefirst material.
 38. The multiple layer injection molded article of claim30 wherein a length of a path in the non-symmetric portion along whichthe at least one first and the at least one second materials flowed toform the molded article differs from a length of any adjacent path by nomore than about 10%.
 39. The multiple layer injection molded article ofclaim 38 wherein a length of a path in the non-symmetric portion alongwhich the at least one first and the at least one second materialsflowed to form the molded article differs from a length of any adjacentpath by no more than about 5%. 40.-73. (canceled)
 74. A multiple layermolded container comprising: a closed end defining a periphery thereofand at least one wall extending from the periphery of the closed enddefining a container sidewall extending completely around the peripheryof the closed end and further defining an open end of the containeropposite the closed end; wherein the closed end and sidewall are formedof first and second materials co-injected at an injection location onthe closed end and generally defining a configuration of the closed endand the sidewall, the second material is substantially contained withinthe first material, the closed end is nonsymmetrical relative to theinjection location, and the open end is enclosable by a substantiallygas impermeable closure to sealingly enclose the container; and whereina length of a path in a non-symmetric portion of the closed end alongwhich the first and second materials flowed to form the molded containerdiffers from a length of any adjacent path by no more than about 15%,and wherein when the container is sealed by said closure, oxygenpermeation into the enclosed container is less than about 0.05 ppm/day.75. The multiple layer molded container of claim 74 wherein the firstmaterial comprises a plastic material including at least one ofpolyethylene, polypropylene, and an adhesive.
 76. The multiple layermolded container of claim 74 wherein the first material and the secondmaterial comprise different materials.
 77. The multiple layer moldedcontainer of claim 74 wherein the second material is relatively more gasimpermeable than the first material.
 78. The multiple layer moldedcontainer of claim 74 wherein the second material comprises at least oneof ethyl vinyl alcohol, nylon, an oxygen scavenging material, and adesiccant.
 79. The multiple layer molded container of claim 74 whereinone of the first material and the second material comprises an adhesive.80. The multiple layer molded container of claim 74 wherein asubstantially gas impermeable closure sealingly encloses the open end ofthe container to form an enclosed container.
 81. The multiple layermolded container of claim 74 wherein oxygen permeation into the enclosedcontainer is less than about 0.005 ppm/day/container.
 82. The multiplelayer molded container of claim 74 containing a substance that degradesupon gaseous exposure.
 83. The multiple layer molded container of claim74 wherein the closure is sealable to the container at a seal contactsurface, and the second material extends throughout at least about 95%of the closed end and sidewall sealable within a boundary defined by theseal contact surface.
 84. The multiple layer molded container of claim83 wherein the closure is sealable to the container at a seal contactsurface, and the second material extends throughout at least about 99%of the closed end and sidewall sealable within a boundary defined by theseal contact surface.
 85. The multiple layer molded container of claim74 wherein a length of a path in the non-symmetric portion of the closedend along which the first and second materials flowed to form the moldedcontainer differs from a length of any adjacent path by no more thanabout 10%.
 86. The multiple layer molded container of claim 85 wherein alength of a path in the non-symmetric portion of the closed end alongwhich the first and second materials flowed to form the molded containerdiffers from a length of any adjacent path by no more than about 5%.87.-121. (canceled)